The present invention concerns self extinguishing polymeric compositions which, upon contacting flame, provide an intumescent char-forming crust, do not produce flame neither toxic fumes, more particularly it concerns the preparation of a synthetic organic compound which contains phosphorus and nitrogen and which, added to synthetic polymers such as polypropylene, or mixtures of such polymer with elastomers and/or with conventional fillers and additives, yield polymeric compositions which when contacting a flame, provide a charforming intumescent crust, and nondropping neither flame nor toxic fumes promoting.
Several processes for making fireproofing or uninflammable polymers are known in the art; such processes are generally based upon the use of metallic compounds, particularly antimony ones, in combination with thermally unstable halogenated compounds, such for example chlorinated paraffin waxes and/or bromided organic compounds.
The art has proposed, to act as flame-retardant and flame barrier several phosphorus containing compounds, for example as disclosed in the U.S. Pat. No. 4,010,137, the diclosure of which is herein referred to.
The combinations "metallic compound+halogenated compound" yields satisfying results as far as the flame-retardant properties conferred thereby to the polymers, but they are subject to serious drawbacks: corrosive phenomena in the mechanism in which the treatment of the materials is performed, and intense outlet of toxic fumes and gases when a fire occurs. Further, acceptable flame retardancy levels are obtained by making use of high concentration of such combinations only.